1. Field of the Invention
The present invention relates to the manufacture of biaxial high modulus materials and, more particularly, to methods and apparatus for continuously converting woven PAN fabric to carbon and graphite products.
2. Description of the Prior Art
High modulus graphite has been available for several years but has not received wide usage because of the high cost and limited availability of the material. Graphite is presently being produced in continuous or discontinuous lengths as fiber filament or yarn. Continuous fiber has a very high cost due to the very high temperatures required for processing coupled with a tendency of the fiber to break during processing under tension and the need for a separate train of equipment for each yarn being processed. The breaking tendency has further precluded the continuous processing of prewoven precursor material.
U.S. Pat. No. 3,803,672 discloses a continuous web process and apparatus for manufacturing high modulus graphite fabric in which precursor fabric is incrementally stretched dynamically followed by preoxidation and graphitization. The application mainly dealt with control of production parameters to develop the high modulus properties in the warp direction of the fabric and the control of the parameters of time, temperature, tension and atmosphere composition during preoxidation to optimize the warp properties while minimizing the possibility of breakage.